1. Field of the Invention
The present invention is directed to height-adjustable columns for furniture, in particular tables.
2. Discussion of the Related Art
The height-adjustable table legs are known to be made of a multi-part column, e. g., a three- or two-part column, the latter consisting of an inner column and an outer column, which are of telescopic design and may be retracted or extended. The outer column may be tightly connected to a base and forms a static unit. The inner column may be connected to the table plate, thereby forming a movable portion of the item of furniture. Typically, drives, which may be operated manually or by electric motor, are disposed within the telescopic column.
Increasingly, however, tables having a height which is adjusted by means of a gas pressure spring provided in one or more table legs are used. Therein, for example, the piston of the gas pressure spring is connected to the static unit of the furniture column and the piston rod of the gas pressure spring is connected to the movable portion such as the table plate or the inner column.
From the prior art according to EP 1 987 734 B1 a table height adjustable by means of a gas pressure spring is known. The table described therein, for which, as an example, two furniture columns are provided, includes an suitable synchronization device, so that a uniform height adjustment of the entire table is also guaranteed when only one gas pressure spring is provided in only one of the columns.
A height-adjustable table having at least one gas pressure spring has, compared to motor-driven adjustable tables, the advantage that the height adjustment can be performed in a much shorter time. Moreover, such a table does not have to be connected to a power supply, saving not only costs but also having a positive effect on the design of the table by omitting any cables.
Before the actual height adjustment of the furniture column, typically a securing means in the form of a lever or a button needs to be actuated. Such a securing means prevents that placing heavy objects on the item of furniture or removing heavy objects from the item of furniture, or a too high or too low load weighing on the table plate during the height adjustment result in an undesired upwards of downwards movement of the furniture column. However, since said height-adjustable items of furniture, in particular tables, sometimes need to carry heavy loads, it is possible that, even when unsecuring the securing means, a sudden drop of the movable portion of the height-adjustable table may occur, possibly resulting in damage to the table or the objects placed thereon or, more importantly, causing injury to the user.
In tables with a gas pressure spring, the latter is usually set to a certain permissible weight above which or below which no height adjustment is possible despite actuation of the securing means, according to the prior art. Advantageously, this weight can be set by means of an additional gas storage which, depending on the wishes of the consumer, can also be arranged on the item of furniture itself.
Moreover, devices are known, wherein the operating lever is connected via a cable system to a locking mechanism, through which the synchronizing means extend. Therein, the locking mechanism measures the tensile forces applied to the synchronization means and enables a height adjustment only if the forces are in equilibrium.
A disadvantage of such systems is, however, that this type of safety measure can be overcome by the user when the user, for example, shakes the movable portion or applies the users' weight to the table plate. If the system is bypassed, a sudden upward or downward movement of the movable portion can occur, which in turn carries large potential for injury.